This invention relates to a gas bag module comprising a module cover.
Known module covers usually swing to the outside when they are opened, the opening flap having a relatively large swiveling radius. This swiveling radius might possibly hurt the occupant sitting too close to the gas bag module, in particular in the case of a so-called out-of-position (OOP) sitting posture of the occupant or in case of a second crash.
The invention provides a gas bag module which has an opening flap that moves less far toward the occupant when it is opened. This is achieved in a gas bag module which comprises a module cover which has at least one opening flap movable upon activation of the module. An axis is provided relative to which the opening flap moves when it is opened, and a tether is provided between the at least one opening flap and a part of the gas bag module. In an open condition of the module cover the opening flap is fixed on the one hand to the module by means of the tether and on the other hand is fixed to the module cover via the axis. The axis and the tether are arranged with respect to the opening flap in such a manner and the opening flap has such a strength that its geometry is changed by the tether when the opening flap swivels open. The opening flap moves outwardly, i.e. toward a passenger compartment by a smaller amount than without the tether. In the gas bag module according to the invention it is the function of the tether to change the geometry of the module cover. This is achieved in that a force, acting on the opening flap e.g. by the deploying gas bag or by some other means, produces a counterforce in the axis and in the tether. The opening flap is preferably bent or even kinked by influencing these forces and counterforces, and in this condition it is moved away from the deployment opening for the gas bag. Caused by the change in the geometry of the opening flap, the latter requires less space during the opening process. When the axis for instance is a pure swiveling axis, the opening flap will have a smaller swiveling radius than without the tether. The term swiveling radius may also be inaccurate in this context, because when the opening flap changes its geometry during the opening movement, any path of movement can be generated for the relevant outer edge of the opening flap.
To ensure that these paths of movement can possibly be predetermined, one or more bending or kinking points in the opening flap have been predefined, which can for instance be produced by a kind of film hinge or some other weakened portions in the cover.
In accordance with the preferred embodiment, the axis is a stationary swiveling axis, which is formed by a film hinge. This formation of the axis is very inexpensive.
The gas bag will usually urge the opening flap, which is formed integrally at the module cover, to the outside and tear open the module cover. It may possibly deliberately press or move the tether such that it causes the geometric deformation of the opening flap. To ensure that this process, namely tearing open, moving the opening flap and the large enough introduction of force to cause the change in geometry, is effected in a predeterminable way, one design of the invention provides a deployment limiting means at the gas bag, which acts at the beginning of the deployment process and directs portions of the gas bag to predetermined points of the tether. The deployment limiting means may for instance be a strap constricting the folded gas bag, which strap will tear during the deployment process, but at the beginning of the deployment process predetermines the initial deployment direction.
In the preferred embodiment, the tether is so short that it exerts a restraining force on the opening flap, which restraining force leads to the change in the geometry of said opening flap, when the deployment opening for the gas bag is open for 20 to 50 percent. This is based on the opening cross-section. It should thus be ensured that the opening flap is bent or kinked already in the initial phase of the opening movement.
In the preferred embodiment, the module cover has an emblem on its outside, the tether being mounted to the inner side of the covering flap in the region of the emblem or so as to be incorporated therein; thus, the tether being able of directly retaining the heaviest part of the cover.